See, we travel as light as possible when going to the beach...and we go a lot.
Towelling hoodie per child, a couple of Foutala/Dock & Bay style towels, picnic blanket perhaps, hat each, sun spray, mini cool bag with water bottles/snacks, goggles, spare swimmers/pants, crocs or wetsuit shoes. Lots of plastic bags to separate wet from dry, use as a bin bag etc. Wipes. If super sunny, some UV brollies that fold small like umbrellas.
A ball, spade, body board.
Kids wear swimmers (plus rash vest) under clothes to go down there, wear whatever water shoes they need, carry their own body board. Everything else just goes in a big beach bag.
Don't scrimp on parking, if the nearest car park charges I pay it not to have to lug everyone back at the end of the day.
I don't take packed lunches, I take loads of snacks (mix of healthy and not) and be prepared to buy something extra, or an ice cream etc. The latter is good bribery for when you leave..."come on then, time to go, we'll grab an ice cream on the way".
We sometimes go all day, but more often then not just for a half day, few hours etc. We can do that cause we're so close, but what we take rarely goes above that.